Definition of Crossopterygii

1: a superorder of Choanichthyes comprising the lobe-finned fishes that have existed since the Devonian but are now largely extinct, that have paired fins somewhat resembling limbs with a scaly axis fringed on one or both sides by dermal rays, and that are generalized fishes in some respects resembling elasmobranchs and in others foreshadowing terrestrial vertebrates which may have evolved from unknown early members of the group — compare latimeria

2in some classifications: a division of fishes coextensive with Choanichthyes or comprising Choanichthyes together with Cladistia — compare actinistia , rhipidistia

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